Hi Folks,
Just sharing a little bit of info about another Jess 4.2 feature:
you'll be able to define inheritance relationships between
deftemplates and between defclasses. Alan Davis was asking about this a
little while ago, and I just had an insight yesterday about how
to do this efficiently.
Anyway, so what this looks like is this:
(deftemplate t1 (slot A) (slot B) (slot C))
(deftemplate t2 extends t1 (slot D) (slot E))
(deftemplate t3 extends t1 (slot F) (slot G))
Now you can write rules which match on patterns of type t1, t2, or
t3. t2 has slots A,B,C,D,E, and t3 has A,B,C,F,G. Furthermore, rules
written to match patterns of type t1 will also match t2 and t3; rules
that match t2 or t3 patterns won't match the other, or t1.
Similarly, with defclasses. I modified my 'pumps' example Beans such
that both Tank and Pump inherit from a new class Machine, with one
property (name). Then you can write
(defclass machine jess.examples.pumps.Machine)
(defclass pump extends machine jess.examples.pumps.Pump)
(defclass tank extends machine jess.examples.pumps.Tank)
and 'machine' rules will match either 'tank' or 'pump' patterns.
Any comments on syntax, ideas for extensions, or subtleties, let me
know. I considered using 'is-a' as COOL does instead of 'extends' -
any opinions one way or the other?
---------------------------------------------------------
Ernest Friedman-Hill
Distributed Systems Research Phone: (510) 294-2154
Sandia National Labs FAX: (510) 294-2234
Org. 8920, MS 9214 [EMAIL PROTECTED]
PO Box 969 http://herzberg.ca.sandia.gov
Livermore, CA 94550
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